Significance Epidemiologically, breast-fed infants contract fewer infections and have infections of shorter duration. These differences may be attributed to differences in composition between breast milk and formula. Lactoferrin (a metal chelate glycoprotein found in human and primate milk) is known to possess antimicrobial activity as well as act against endotoxin induced inflammation. Additionally, lactoferrin may indirectly suppress pathogenic colonization by encouraging an environment more suitable for growth of more "host-friendly" bacteria. Thus the presence of lactoferrin in milk may account, in part, for the breast-fed infant's ability to withstand infection. Therefore, supplementation of infant formula with lactoferrin may help protect formula-fed infants from microbiologic infection. Objectives To feed infant monkeys formula supplemented with lactoferrin, inoculate them with a strain of E. coli and assess their ability to resist the infection and recolonize the intestine with Bifidobacteria and Lactobacilli. Results The intestinal flora of breast-fed monkeys differs from that of formula-fed monkeys in that formula-fed monkeys have a predominance of E. coli and breast-fed monkeys have a predominance of Lactobacilli. Additionally, lactoferrin seemed to prevent an increase in E. coli colonization while stimulating the colonization with Bifidobacteria or Lactobacilli. Future Directions To evaluate the effects of other prebiotics on various pathogens. KEY WORDS lactoferrin, E. coli, pathogens, prebiotic, infant nutrition FUNDING Private Sector